414 Anions and Aromatic Rings: Fluorescent Signaling and Attractive Interactions?

Friday, November 6, 2009: 9:00 AM
Rio Grande (Camino Real Hotel)
Darren W. Johnson , Department of Chemistry, University of Oregon, Eugene, OR
Michael M. Haley , Department of Chemistry, University of Oregon, Eugene, OR
This talk will focus on two areas of research in the area of anion binding: 1) designing receptors to utilize the attractive interaction between anions and aromatic rings, and 2) developing modular, inherently fluorescent receptors for anions.  Increasing attention has been paid to understanding of the emerging attraction between anions and electron-deficient arenes.  Strategies for designing receptors that bring multiple arenes to bear on a single anion, anion binding selectivity of the receptors, and the nature of the different interaction types between anions and arenes will be discussed.  Numerous theoretical and solid state studies have shown the existence of an attraction between anions and electron-deficient aromatics; however, there are few reports of this interaction observed in solution, and in even fewer cases have association constants been reported.  Preliminary efforts to quantify the strength and selectivity of this new binding motif for anions in solution will be discussed.  In addition, a series of new fluorescent anion receptors based on a functionalized 2,6-alkynylpyridine scaffold will also be described, including a sulfonamide-functionalized receptor that forms a 2:2 dimer with both water or halides (Cl-, Br-) depending on the protonation state of the pyridine ring.  This is a rare example of both halides and water molecules serving the same structural hydrogen bonding roles in a synthetic self-assembled system.  This receptor class also exhibits tunable fluorescence in the presence of anions, and preliminary applications using this feature of the receptors will be described.
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